For some reason people get all bent out of shape by this sentence. But no one seems to get upset when a demographer describes them as middle-class, American, employed, or retired. Descriptive labels of a class of people (or objects or animals...) don't necessarily depend on the members of that class identifying using that descriptive label. Flamingos don't have to identify as flamingos in order for a biologist to lable them "flamingos."

But describing cisgender people with the label "cisgender" raises cisgender people's hackles, which tells us a lot about the power and privilege of passing as unmarked and unnamed: which is exactly the point of the piece. Equality (in naming) only feels "oppressive" to those who have lived a life privileged by being unnamed. Being treated equally and having your gender named isn't the same as being "oppressed." Welcome to the world the rest of us live in!